It has previously been proposed to provide hybrid circuit networks in flip-chip technology. This technology refers to placing a semiconductor chip opposite a ceramic substrate which has metallic circuits thereon, and connecting the chip to the substrate by fusing a contact element, which may be spherical, between the pads of the chip and the substrate, see for example the referenced U.S. Pat. No. 3,292,240, McNutt et al. The solder in form of a small solder dot is customarily a lead-tin soft solder.
This technology, referred to as "flip-chip" or face-to-face technology since the chip or the substrate, respectively, are flipped above each other, has been improved, as described in U.S. Pat. No. 3,517,279, Ikeda, by not using tiny metal spheres or balls and rather applying a soft solder layer on the respective contact elements on the chip and/or the substrate, and then soldering the chip on the substrate by a re-flow solder process, utilizing the previously applied solder layer.
U.S. Pat. No. 2,303,393, Hymes, describes a connection method and system which is an improvement over that of U.S. Pat. No. 3,292,240, in that the terminal elements or pads are characterized as being essentially non-deformable, even if they are subjected to high temperature.
The connection arrangements described are difficult to make if the packing density of the lines is high, since the connection must be mechanically and electrically perfect, without, however, causing short circuit between adjacent lines. It is difficult to apply soft solder to the connection metallization lines of the semiconductor chip and/or the pads of the carrier substrate in such a quantity that, upon melting, the electrical connection will be excellent without, however, causing short circuits. Semiconductor elements which have very small, and closely spaced electrical contact metallization regions, can, therefore, be connected by the known flip-chip technology only with some limitations based on the geometric placement of the connection lines and the connection pads.